a-lungimea drumului
I zi: a-1/4xa=a-a/4=(4a-a)/4=3a/4
II zi : 3a/4-(5/6)x(3a/4)=(3ax6-5x3a)/24=(18a-15a)/24=3a/24=simplif=a/8
a/8=25
a=25x8
a=200 km lungimea drumului
in I zi a parcurs:200x1/4=200/4=50km
II zi: (200-50)x5/6=150x5/6=125km
III zi :25km
50+125+25=200km
